NO Initial ITS Start location: l3 Program variables: x^0 0: l0 -> l1 : x^0'=x^post1, (0 == 0 /\ -1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 1: l1 -> l0 : x^0'=x^post2, -x^post2+x^0 == 0, cost: 1 2: l2 -> l0 : x^0'=x^post3, (0 == 0 /\ 2-x^post3 <= 0), cost: 1 3: l3 -> l2 : x^0'=x^post4, x^0-x^post4 == 0, cost: 1 Chained Linear Paths Start location: l3 Program variables: x^0 5: l0 -> l0 : x^0'=x^post2, (0 == 0 /\ -1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ -x^post2+x^post1 == 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 4: l3 -> l0 : x^0'=x^post3, (0 == 0 /\ 2-x^post3 <= 0 /\ x^0-x^post4 == 0), cost: 1 Eliminating location l2 by chaining: Applied chaining First rule: l3 -> l2 : x^0'=x^post4, x^0-x^post4 == 0, cost: 1 Second rule: l2 -> l0 : x^0'=x^post3, (0 == 0 /\ 2-x^post3 <= 0), cost: 1 New rule: l3 -> l0 : x^0'=x^post3, (0 == 0 /\ 2-x^post3 <= 0 /\ x^0-x^post4 == 0), cost: 1 Applied deletion Removed the following rules: 2 3 Eliminating location l1 by chaining: Applied chaining First rule: l0 -> l1 : x^0'=x^post1, (0 == 0 /\ -1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 Second rule: l1 -> l0 : x^0'=x^post2, -x^post2+x^0 == 0, cost: 1 New rule: l0 -> l0 : x^0'=x^post2, (0 == 0 /\ -1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ -x^post2+x^post1 == 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 Applied deletion Removed the following rules: 0 1 Simplified Transitions Start location: l3 Program variables: x^0 7: l0 -> l0 : x^0'=x^post1, (-1-x^post1 <= 0 /\ -1+x^post1 <= 0), cost: 1 6: l3 -> l0 : x^0'=x^post3, 2-x^post3 <= 0, cost: 1 Propagated Equalities Original rule: l3 -> l0 : x^0'=x^post3, (0 == 0 /\ 2-x^post3 <= 0 /\ x^0-x^post4 == 0), cost: 1 New rule: l3 -> l0 : x^0'=x^post3, (0 == 0 /\ 2-x^post3 <= 0), cost: 1 propagated equality x^post4 = x^0 Simplified Guard Original rule: l3 -> l0 : x^0'=x^post3, (0 == 0 /\ 2-x^post3 <= 0), cost: 1 New rule: l3 -> l0 : x^0'=x^post3, 2-x^post3 <= 0, cost: 1 Propagated Equalities Original rule: l0 -> l0 : x^0'=x^post2, (0 == 0 /\ -1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ -x^post2+x^post1 == 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 New rule: l0 -> l0 : x^0'=x^post1, (0 == 0 /\ -1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 propagated equality x^post2 = x^post1 Simplified Guard Original rule: l0 -> l0 : x^0'=x^post1, (0 == 0 /\ -1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 New rule: l0 -> l0 : x^0'=x^post1, (-1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 Eliminated Temporary Variables via Transitive Closure Original rule: l0 -> l0 : x^0'=x^post1, (-1-x^post1 <= 0 /\ 2-x^1 <= 0 /\ 1-x^1 <= 0 /\ -1+x^post1 <= 0), cost: 1 New rule: l0 -> l0 : x^0'=x^post1, (-1-x^post1 <= 0 /\ -1+x^post1 <= 0), cost: 1 Step with 6 Trace 6[(2-x^post3 <= 0)] Blocked [{}, {}] Step with 7 Trace 6[(2-x^post3 <= 0)], 7[(-1-x^post1 <= 0 /\ -1+x^post1 <= 0)] Blocked [{}, {}, {}] Nonterm Start location: l3 Program variables: x^0 7: l0 -> l0 : x^0'=x^post1, (-1-x^post1 <= 0 /\ -1+x^post1 <= 0), cost: 1 8: l0 -> LoAT_sink : (1+x^post1 >= 0 /\ -1+n >= 0 /\ 1-x^post1 >= 0), cost: NONTERM 6: l3 -> l0 : x^0'=x^post3, 2-x^post3 <= 0, cost: 1 Certificate of Non-Termination Original rule: l0 -> l0 : x^0'=x^post1, (-1-x^post1 <= 0 /\ -1+x^post1 <= 0), cost: 1 New rule: l0 -> LoAT_sink : (1+x^post1 >= 0 /\ -1+n >= 0 /\ 1-x^post1 >= 0), cost: NONTERM 1+x^post1 >= 0 [0]: monotonic increase yields 1+x^post1 >= 0 1-x^post1 >= 0 [0]: monotonic increase yields 1-x^post1 >= 0 Replacement map: {1+x^post1 >= 0 -> 1+x^post1 >= 0, 1-x^post1 >= 0 -> 1-x^post1 >= 0} Step with 8 Trace 6[(2-x^post3 <= 0)], 8[(1+x^post1 >= 0 /\ -1+n >= 0 /\ 1-x^post1 >= 0)] Blocked [{}, {}, {8[T]}] Refute Counterexample [ x^0=2 ] 6 [ x^0=x^0 ] 8 NO Build SHA: a05f16bf13df659c382799650051f91bf6828c7b